The National Institute of Mental Health in conjunction with the Laboratory of Experimental Therapeutics, NINCDS; Michigan Osteopathic Medical Center, Child and Youth Mental Health Hospital and the Tourette and Tic Laboratory and Clinic of Mount Sinai Hospital are examining of blink rate in a variety neuropsychiatric disorders. In medication-free patients with movement disorders blink rate is decreased in those patients with parkinsonism or progressive nuclear palsy but not increased in several hyperkinetic states including dystonia, tardive dyskinesia and Tourette's syndrome. In the parkinsonian patients the blink rate correlates with the severity of the illness. Patients with schizophrenia who have been withdrawn from medication have a slight but statistically significant increase in their blink rate. This increase is primarily seen in the spring-summer period. Moreover, never medicated adolescent inpatients with "psychosis" have an increased blink rate compared to their nonpsychotic counterparts, indicating that increased blinking may precede treatment. Finally compared with normal children of the same age blink rate is increased in autistic children but decreased in children with mental retardation. We have attempted to link blink rate to central dopamine activity and explain these differences with regard to alterations of dopamine activity in the various disorders.